"My hands were frozen on the handlebars but winning the title certainly made me feel warm inside," Groombridge said.
King's elder brother Darryll (Yamaha) won the 250cc two-stroke class but was out of luck in the veterans over-35 division after crashing out of one of the races. Taranaki's Greg Ngeru (Honda) won the class ahead of Auckland super motard specialist Toby Summers (Yamaha).
Taupo's Rodney Tomblin (Honda) won the over-40 veterans class.
Cameron Dillon (Honda) won the junior 12-16 years (125cc two-stroke and 250cc four-stroke) class, while fellow Mangakino rider Kayne Lamont (Yamaha) was runner-up. Lamont also tasted success in the 13-16 years (85cc two-stroke) class when he won the title ahead of fellow Yamaha rider Logan Blackburn. Otago's Courtney Duncan (Honda) won the 8-12 years 85cc class ahead of Atiamuri's Dion Picard (Suzuki).
The four-wheeled action was dominated by national ATV champion Quentin Palmer, the Suzuki rider from Taumarunui coming from behind to battle past Amberley's Ian Ffitch (Honda) for the open class ATV title.
Pukekohe teenager Annelise Kiely won the junior ATC title.